No addons, Cache, WTF and Interface folders removed, game restarted.
Target mobs are not highlighted. Trying to look at the quest text in the quest log gives the following error (too long to go into an in-game bug report):
Message: Interface/FrameXML/QuestInfo.lua:583: Usage: IsSpellKnownOrOverridesKnown(spellID[, isPet])
Time: Thu Mar 30 08:51:29 2023
Count: 2
Stack: Interface/FrameXML/QuestInfo.lua:583: Usage: IsSpellKnownOrOverridesKnown(spellID[, isPet])
[string “=[C]”]: in function IsSpellKnownOrOverridesKnown' [string "@Interface/FrameXML/QuestInfo.lua"]:583: in function ?’
[string “@Interface/FrameXML/QuestInfo.lua”]:99: in function QuestInfo_Display' [string "@Interface/FrameXML/QuestMapFrame.lua"]:612: in function QuestMapFrame_ShowQuestDetails’
[string “@Interface/FrameXML/QuestMapFrame.lua”]:1710: in function <Interface/FrameXML/QuestMapFrame.lua:1692>
Locals: (*temporary) = nil